全文获取类型
收费全文 | 97242篇 |
免费 | 17379篇 |
国内免费 | 23583篇 |
专业分类
化学 | 70519篇 |
晶体学 | 2464篇 |
力学 | 6701篇 |
综合类 | 2221篇 |
数学 | 14189篇 |
物理学 | 42110篇 |
出版年
2024年 | 195篇 |
2023年 | 1172篇 |
2022年 | 2868篇 |
2021年 | 3063篇 |
2020年 | 3274篇 |
2019年 | 3408篇 |
2018年 | 3052篇 |
2017年 | 3610篇 |
2016年 | 3879篇 |
2015年 | 4713篇 |
2014年 | 5720篇 |
2013年 | 7384篇 |
2012年 | 8025篇 |
2011年 | 9537篇 |
2010年 | 7793篇 |
2009年 | 7924篇 |
2008年 | 8357篇 |
2007年 | 7239篇 |
2006年 | 6938篇 |
2005年 | 5881篇 |
2004年 | 5331篇 |
2003年 | 3892篇 |
2002年 | 3992篇 |
2001年 | 3518篇 |
2000年 | 3309篇 |
1999年 | 2188篇 |
1998年 | 1479篇 |
1997年 | 1207篇 |
1996年 | 1126篇 |
1995年 | 947篇 |
1994年 | 862篇 |
1993年 | 1108篇 |
1992年 | 997篇 |
1991年 | 761篇 |
1990年 | 706篇 |
1989年 | 646篇 |
1988年 | 385篇 |
1987年 | 288篇 |
1986年 | 264篇 |
1985年 | 187篇 |
1984年 | 172篇 |
1983年 | 153篇 |
1982年 | 94篇 |
1981年 | 79篇 |
1980年 | 58篇 |
1979年 | 74篇 |
1978年 | 35篇 |
1977年 | 27篇 |
1965年 | 26篇 |
1959年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
43.
Aequationes mathematicae - We discuss equivalence conditions for the non-existence of non-trivial meromorphic solutions to the Fermat Diophantine equation $$f^m(z)+g^n(z)=1$$ with integers $$m,n\ge... 相似文献
44.
Metabolic profiles of dioscin in rats revealed by ultra‐performance liquid chromatography quadrupole time‐of‐flight mass spectrometry 下载免费PDF全文
He Zhu Jin‐Di Xu Qian Mao Hong Shen Ming Kong Jian‐Ping Chen Song‐Lin Li 《Biomedical chromatography : BMC》2015,29(9):1415-1421
Dioscin (DIS), one of the most abundant bioactive steroidal saponins in Dioscorea sp., is used as a complementary medicine to treat coronary disease and angina pectoris in China. Although the pharmacological activities and pharmacokinetics of DIS have been well demonstrated, information regarding the final metabolic fates is very limited. This study investigated the in vivo metabolic profiles of DIS after oral administration by ultra‐performance liquid chromatography quadrupole time‐of‐flight mass spectrometry method. The structures of the metabolites were identified and tentatively characterized by means of comparing the molecular mass, retention time and fragmentation pattern of the analytes with those of the parent compound. A total of eight metabolites, including seven phase I and one phase II metabolites, were detected and tentatively identified for the first time. Oxidation, deglycosylation and glucuronidation were found to be the major metabolic processes of the compound in rats. In addition, a possible metabolic pathway on the biotransformation of DIS in vivo was proposed. This study provides valuable and new information on the metabolism of DIS, which will be helpful for further understanding its mechanism of action. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
45.
46.
分析学生对二氧化碳的3个典型学科认知障碍,以“二氧化碳的捕捉”为情境,通过“尝试捕捉二氧化碳”“谁在捕捉二氧化碳”“捕捉背后的原理”等3个主要环节,实现对学科认知障碍的突破,展示了一种新的中考复习教学思路。 相似文献
47.
基于深度学习的方法,在HL-2A装置上开发出了一套边缘局域模(ELM)实时识别算法。算法使用5200次放电数据(约24.19万数据切片)进行学习,得到一个深度为22层的卷积神经网络。为衡量算法的识别能力,识别了HL-2A装置自2009年实现稳定ELMy H模放电以来所有历史数据(约26000次放电数据),共识别出1665次H模放电,其中误识别35次,误报率为2.10%。在实际的1634次H模放电中,漏识别4次,漏识别率为0.24%。该误报率和漏报率可以满足ELM实时识别的精度要求。识别算法在实时控制环境下,对单个时间点的平均计算时间为0.46ms,可以满足实时控制的计算速度要求。 相似文献
48.
Nonlinear Dynamics - Global dynamics of a flexible asymmetrical rotor resting on vibrating supports is investigated. Hamilton’s principle is used to derive the partial differential governing... 相似文献
49.
Understanding and control of the surface properties such as molecular orientations are of great importance in numerous applications of ionic liquids. However, there remain discrepancies among the previous experimental and theoretical studies on the surface orientation and structures of room temperature ionic liquids(RTIL) systems. In this article, the orientation of 1-butyl-3-methylimidazolium([bmin]) cation at the air/liquid interface of a characteristic RTIL, 1-butyl-3-methylimidazolium hexafluorophosphate([bmim][PF6]), was investigated by the sum frequency generation vibrational spectroscopy(SFG-VS). Detailed polarization and experimental configuration analyses of the SFG-VS spectra showed the possibility of a small spectral splitting in the CH3 symmetric stretching region, which can be further attributed to the probable existence of multiple orientations for the interfacial [bmim] cations. In addition, the(N)–CH3 vibrations were absent, ruling out the prediction by several recent molecular dynamics simulations which state that portions of the [bmim] cations orient with a standing-up(N)–CH3 group at the ionic liquid surface. Hence, new realistic theoretical models have to be developed to reflect the complex nature of the ionic liquid surface. 相似文献
50.
Hyper-parallel quantum information processing is a promising and beneficial research field. Herein, a method to implement a hyper-parallel controlled-phase-flip (hyper-CPF) gate for frequency-, spatial-, and time-bin-encoded qubits by coupling flying photons to trapped nitrogen vacancy (NV) defect centers is presented. The scheme, which differs from their conventional parallel counterparts, is specifically advantageous in decreasing against the dissipate noise, increasing the quantum channel capacity, and reducing the quantum resource overhead. The gate qubits with frequency, spatial, and time-bin degrees of freedom (DOF) are immune to quantum decoherence in optical fibers, whereas the polarization photons are easily disturbed by the ambient noise. 相似文献